Apparent Weight (Apparent weight, friction, drag)

apparent weight

• scale measures how hard the object is pushing on it — this push is the normal force Fn

• the scale assumes the object is sitting on it in equilibrium so Fn = mg

• the scale is calibrated to report m = Fn/g

• doesnt apply when object is accelerating vertically (ex. in an elevator) bc object is not in equilibrium

the objects normal force Fn

what force is measured when an object is “pushing” on a scale?

the magnitude of the normal force acting on you is your apparent weight

remember: the magnitude of the normal force acting on you is your apparent weight

how heavy you FEEL

what is your apparent weight?

Fnet is also upwards

in an elevator that is accelerating upwards in what direction is the Fnet?

Fn > W

in an elevator that is accelerating upwards which is larger Fn or W?

Fnet = ma = Fn - w

in an elevator that is accelerating upwards what is the magnitude of the Fnet?

Apparent weight = Fn

Apparent weight = Fn

Fn = w + ma

in an elevator that is accelerating upwards what is the apparent weight?

if Fn > W then you feel heavier than usual - apparent weight is more

if Fn > W?

the more your’e accelerating upwards, the heavier you feel

remember: the more your’e accelerating upwards, the heavier you feel 

Fnet is also downwards 

in an elevator that is accelerating downwards in what direction is the Fnet?

W > Fn 

in an elevator that is accelerating downwards which is larger Fn or W? 

Fnet = ma = W - Fn

in an elevator that is accelerating downwards what is the magnitude of the Fnet?

Fn = W - ma

in an elevator that is accelerating downwards what is the apparent weight?

if Fn < W then you feel lighter than usual - apparent weight is less 

if Fn < W? 

the more your’e accelerating downwards, the lighter you feel

remember: the more your’e accelerating downwards, the lighter you feel